The present invention relates to a keyboard musical instrument with a transpositional function capable of designating an interval to be transposed by utilizing keyboard's keys.
A conventional keyboard musical instrument with a transpositional function is described in Japanese Patent Prepublication No. 55-126296. This musical instrument includes a rotary switch for designating an interval to be transposed by operating a rotary switch. When a player selects a certain one among twelve notes, an encoder following the rotary switch outputs transposition data having a value corresponding to the designated interval which is the difference between the selected note and note C on a C major scale.
In the conventional keyboard musical instrument with a transpositional function described above, a 12-contact rotary switch for designation of twelve notes must be mounted on a keyboard musical instrument, resulting in a high-cost keyboard musical instrument. In addition, the 12-contact rotary switch cannot specify any interval exceeding one octave, thus limiting the interval to be transposed to 12 degrees. It would be possible to designate an interval exceeding one octave by increasing the number of contacts of the rotary switch. However, the increase in the number of contacts leads to a high fabrication cost of the rotary switches. Accordingly, in an available rotary switch, the number of contacts thereof is limited. As a result, the quantity to be transposed cannot be greatly increased.